Work vehicles such as construction, forestry, mining and agricultural work vehicles may employ the use of an electronically controlled ride control system to minimize bouncing and vibration of the vehicle as it traverses over uneven or rough terrain. Ride control can improve the bouncing and vibration of the operator, and also may have safety implications as the operator manually operates hydraulically and electrically controlled functions of the vehicle. One way of implementing ride control is to measure the relative displacement between the vehicle chassis and axles as the vehicle moves over the uneven or rough terrain. This can be measured directly, or inferred by measuring the displacement of the suspension strut associated with each attachment location between the vehicle chassis and axle.
A commonly used method for measuring the displacement of a suspension strut is to place a sensor between the axle or axle assembly and the vehicle frame. This is usually achieved by placing a rotary sensor with a lever arm that extends from it, near or on the vehicle's frame, and then having a linkage system connect the lever arm to the axle assembly. Because the axle is often the lowest structural part of the vehicle, it has a tendency to drag through mud in very muddy applications. This means that the linkage system is prone to damage from the mud or debris that flows over the axle.
This method of sensing is needed because the suspension struts of vehicles that have strut displacement sensors, have the strut barrel attached to the vehicle chassis, and the rod section attached to the axle assembly. Since the barrel is a fixed length, while the exposed rod section changes with strut displacement, the strut displacement needs to be measured between the barrel end (or vehicle chassis) and the rod end (or the axle assembly), which forces parts of the sensor into the debris flow zone.
The manufacturer Bell Equipment senses vehicle strut displacement by measuring between the vehicle chassis and the axle assembly. The Bell Equipment design attempts to protect the sensor linkage system by using heavy brackets that elevate the linkage connection higher off the axle so that it is out of the debris flow. This design still leaves the brackets prone to damage, and since the linkage is still relatively low, they are still in danger of being damaged.
The manufacturer Volvo places the strut sensor linkage lower down toward the axle, where it is more vulnerable to debris flow. The Volvo design uses a much sturdier (and therefore more expensive) linkage arrangement in an effort to protect it from damage.
Other methods to protect the displacement sensor might be to place the sensor inside the strut, or use magnetic sensors to measure the position of the piston within the strut. These technologies are commonly used to measure the displacement of hydraulic cylinders, but are expensive and would complicate the strut design considerably.
What is needed in the art is a suspension strut measurement system and method which effectively allows the displacement of the strut to be measured, while minimizing damage to the measurement system during operation of the work vehicle.